Raspberry Pi Balloon Goes Too High, Goes Boom, But Survives

Some people like to get high on a Wednesday afternoon. [Kevin Hubbard] of Black Mesa Labs likes to get really high. Even higher than intended: last month, he flew a helium balloon powered by a Raspberry Pi to 103,000 feet. It was only supposed to go to 90,000, but a fault in the code for the controller meant that it went higher, burst and plunged to the ground. All thanks to an extra hash mark in his code.

[Kevin] was part of a team called the Balloongineers who are competing in the Global Space Balloon Challenge, a project to simultaneously fly balloons from multiple locations. The Balloongineers entry was called HAB1, built around a Raspberry Pi, an FPGA watchdog system, a uBlox GPS and an Iridium satellite modem. The idea was that their balloon would zoom up to 90,000 feet, where it would release some helium gas, hover, and move eastwards with the prevailing winds. reporting back via satellite as it went. Unfortunately, something went wrong. The balloon didn’t report back properly, and kept on rising, eventually reaching over 100,000 feet, where it burst and fell to earth.

[Kevin] thought all was lost, including the expensive satellite modem that HAB1 used. But the next day, his balloon sent him an email, reporting that it was hale and hearty at an altitude of 300 feet. After recovery, he analyzed HAB1, and figured out what had happened: a single mistyped hash mark had caused the system to lock up when it tried to open the vent to release the gas.

What saved the rig was the foresight [Kevin] had in building it. Although the system didn’t work fully as planned, the FPGA watchdog (nicknamed the Lizard Brain) eventually noticed that the main computer was locked up, and rebooted it, enabling the system to report back to [Kevin]. An additional recovery mode woke the system once an hour sent a location and went back to sleep, which allowed the small battery to keep powering the system until it could get a signal out the morning after. That’s a smart piece of design in a system that allowed them to recover the hardware, even though the main objective of hovering at 90,000 feet wasn’t achieved.

[Kevin] ends his writeup of the flight with a few notes that any engineer would be wise to consider. Primary among these is his decision to have the system check very rarely for manual overrides over the satellite connection. He decided to do this to save money: checking for messages on Iridium costs a certain amount each time you do it. If he had checked more frequently, he might have been able to fix the problem earlier by venting the helium manually, leading to a more controlled descent and recovery. In any project, a failure can only be useful if you can figure out what the problem was, gathering as much information as possible to help you avoid it next time.

20 thoughts on “Raspberry Pi Balloon Goes Too High, Goes Boom, But Survives

  1. I’ve been wondering if these balloons can have a ballast system that uses solar power and electrolysis, and possibly even a Peltier driven condenser unit to perpetually control their buoyancy right across the negative to positive range. If you need to go up you turn water into hydrogen and vent the oxygen, to go down you run some of your hydrogen through a fuel cell to capture it back as water, using ambient air for the oxygen.

      1. One that is made of a strong material, such as mylar, that will not expand. So when the gas inside reaches the same density as the surrounding air, it has no additional lift. IIRC, they are called super pressure balloons.

  2. I’m just impressed the damn thing fell 100,000 feet and survived, drop a smart phone a foot and your buying a new smart phone! Maybe he should have ground tested the helium release first, feed in false data to test for proper helium farting.

  3. Yes, you can carry ballast, as well as vent gas, to control your altitude.

    We flew our prototype cosmic ray anisotropy telescope on a 1,000,000 cu ft balloon from National Center for Atmospheric Research (NCAR) north of Dallas,TX. Our package was about 100 lb., but the NCAR package was 200 kg (440 lbs) mostly water ballast. On day 1, we flew east about 2000 miles and out over the Atlantic (bad!) at 280,000 feet. So, NCAR vented gas, dropping to 230,000 feet, and we rode WNW winds back to Colorado. Then they dumped ballast water rising to 290,000 ft, and caught winds to carry us back to Oklahoma, where the packages were cut down and retrieved by NCAR.at the end of day 2 (as scheduled). With ballast, gas vent, and good high altitude wind data, you can actually navigate pretty darn well!

    1. Are those numbers right?

      For my PhD work (long time ago, so my numbers may be off) we flew a Gamma Ray Telescope.
      3000 lbs + ballast, IIRC, on a 23 million cubic foot balloon. We got up to 120,000 ft, which is about 4 millibars pressure. Bigger balloon, but much bigger payload. Still, a factor of two in altitude squares the pressure ratio (very roughly), so 240kft would be 16 microbars, and almost no buoyancy.

      1. You’re right to be skeptical. As far as I know, the high altitude balloon record is around 53 km (~173,000 ft). I doubt someone almost doubled the record, especially with a 100 lb payload.

  4. I always thought it would be better to have a small compressor and helium tank on board. To go up let helium out of the tank and into the balloon. To go down compress helium back into the tank.

  5. 100,000 foot is about 30km.
    290,000 foot is about 88km – just over half the 160km minimum distance required for Low Earth Orbit (LEO).

    For those who are curious, but thrown by the non-metric measurements commonly used for altitude.

    1. Knowing, knowing why and how, yet it still staggers me to think the atmosphere is to thin. [ and it’s apparently so difficult for us to leave this rock. ]
      Maybe we will learn how to stay still and let the Earth drop out from under us one day :D

  6. As I watched the video, in the beginning all I could think wasn’t about the flight or the fact it made it to the ground safely. Nope, I was obsessed with the two jerks who parked taking up two spaces.. One ON the line and one diagonally across two parking spaces.. I hate people like that. Just saying.. Caption should read “unmanned balloon captures pair of goofs who can’t park;explodes and returns to Earth to offer proof”.

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